Just Accepted

Display Method:

Published:
Abstract:
The spectroscopic parameters and decay channels of the axial-vector tetraquark \begin{document}$T_{bb;\overline{u}\overline{s}}^{-}$\end{document} (in what follows \begin{document}$T_{b:\overline{s}}^{\mathrm{AV}}$\end{document} ) are explored by means of the QCD sum rule method. The mass and coupling of this state are calculated using the two-point sum rules by taking into account various vacuum condensates up to dimension 10. Our prediction for the mass of this state \begin{document}$m = (10215\pm 250)\; \mathrm{MeV}$\end{document} confirms that it is stable against strong and electromagnetic decays, and can dissociate to conventional mesons only through weak transformations. We investigate the dominant semileptonic \begin{document}$T_{b:\overline{s}}^{\mathrm{AV}} \to {\cal{Z}}_{b:\overline{s}}^{0}l\overline{\nu}_l$\end{document} and nonleptonic \begin{document}$T_{b:\overline{s}}^{\mathrm{AV}} \to {\cal{Z}}_{b:\overline{s}}^{0}M$\end{document} decays of \begin{document}$T_{b:\overline{s}}^{\mathrm{AV}}$\end{document} . In these processes \begin{document}${\cal{Z}}_{b:\overline{s}}^{0}$\end{document} is a scalar tetraquark \begin{document}$[bc][\overline{u}\overline{s}]$\end{document} built of a color-triplet diquark and antidiquark, whereas M is one of the vector mesons \begin{document}$\rho ^{-}$\end{document} , \begin{document}$K^{\ast}(892)$\end{document} , \begin{document}$D^{\ast }(2010)^{-}$\end{document} , and \begin{document}$D_{s}^{\ast -}$\end{document} . In order to calculate partial widths of these decays, we make use of the QCD three-point sum rule approach and evaluate weak transition form factors \begin{document}$G_{i}$\end{document} , \begin{document}$i = 0.1,2,3$\end{document} , which govern these processes. The full width \begin{document}$\Gamma _{\mathrm{full}} = (12.9\pm 2.1)\times 10^{-8}\; \mathrm{MeV}$\end{document} , and mean lifetime \begin{document}$\tau = 5.1_{-0.71}^{+0.99}\; \mathrm{fs}$\end{document} of the tetraquark \begin{document}$T_{b:\overline{s}}^{\mathrm{AV}}$\end{document} are computed using aforementioned weak decays. Obtained information on parameters of \begin{document}$T_{b:\overline{s}}^{\mathrm{AV}}$\end{document} and \begin{document}${\cal{Z}}_{b:\overline{s}}^{0}$\end{document} is useful for experimental investigations of these double-heavy exotic mesons.
Published:
Abstract:
We construct a new global optical model potential to describe the elastic scattering of 12C. The experimental data of elastic-scattering angular distributions and total reaction cross sections for targets from 24Mg to 209Bi are simultaneously considered below 200 MeV within the framework of the optical model. The results calculated using the derived global optical potential are compared with the existing experimental data. The reliability of the global optical potential is further tested by predicting the elastic scattering data out of the mass and energy ranges, within which the global potential parameters are determined, and reasonable results are also obtained.
Published:
Abstract:
The minimal \begin{document}${\rm{U}}(1)_{\rm{{B-L}}}$\end{document} extension of the Standard Model (B-L-SM) offers an explanation for neutrino mass generation via a seesaw mechanism as well as contains two new physics states such as an extra Higgs boson and a new \begin{document}$Z'$\end{document} gauge boson. The emergence of a second Higgs particle as well as a new \begin{document}$Z^\prime$\end{document} gauge boson, both linked to the breaking of a local \begin{document}${\rm{U}}(1)_{\rm{{B-L}}}$\end{document} symmetry, makes the B-L-SM rather constrained by direct searches at the Large Hadron Collider (LHC) experiments. We investigate the phenomenological status of the B-L-SM by confronting the new physics predictions with the LHC and electroweak precision data. Taking into account the current bounds from direct LHC searches, we demonstrate that the prediction for the muon \begin{document}$\left(g-2\right)_\mu$\end{document} anomaly in the B-L-SM yields at most a contribution of approximately \begin{document}$8.9 \times 10^{-12}$\end{document} which represents a tension of \begin{document}$3.28$\end{document} standard deviations, with the current \begin{document}$1\sigma$\end{document} uncertainty, by means of a \begin{document}$Z^\prime$\end{document} boson if its mass lies in a range of \begin{document}$6.3$\end{document} to \begin{document}$6.5\; {\rm{TeV}}$\end{document} , within the reach of future LHC runs. This means that the B-L-SM, with heavy yet allowed \begin{document}$Z^\prime$\end{document} boson mass range, in practice does not resolve the tension between the observed anomaly in the muon \begin{document}$\left(g-2\right)_\mu$\end{document} and the theoretical prediction in the Standard Model. Such a heavy \begin{document}$Z^\prime$\end{document} boson also implies that the minimal value for a new Higgs mass is of the order of 400 GeV.
Published:
Abstract:
The experimental cross sections for the 94Zr(n,d*)93m+gY, 96Zr(n,γ)97Z, 96Zr(n,2n)95Zr, 90Zr(n,α)87mSr, 94Zr(n,α)91Sr,90Zr(n,p)90mY, 92Zr(n,p)92Y and 94Zr(n,p)94Y reactions have been measured in the neutron energy range of 13.5-14.8 MeV by means of the activation technique. The neutrons were produced through the D-T reaction. A high-purity germanium detector with high energy resolution was used to measure the induced γ activities. In combination with the nuclear reaction theoretical models, the excitation curves concerning the above-mentioned eight nuclear reactions within the incident neutron energy range from the threshold to 20 MeV were gained by adopting the nuclear theoretical model program system Talys-1.9. The obtained experimental cross sections were analyzed and compared with the experimental data taken from published literatures and the results calculated by using Talys-1.9. The results show that our experimental results agree with some previous experimental values as well as those of theoretical excitation curve at the corresponding energies, and the theoretical excitation curves obtained can match the experimental data well in general.
Published:
Abstract:
In this paper we study the symmetry energy and the Wigner energy in the binding energy formula for atomic nuclei. We extract simultaneously the \begin{document}$I^2$\end{document} symmetry energy and Wigner energy coefficients by using the double difference of "experimental" symmetry-Wigner energies, based on the binding energy data of nuclei with \begin{document}$A \geq 16$\end{document}. Our study of the triple difference formula and the "experimental" symmetry-Wigner energy suggests that the macroscopic isospin dependence of binding energies is well explained by the \begin{document}$I^{2}$\end{document} symmetry energy and the Wigner energy, and further considering the \begin{document}$I^{4}$\end{document} term in the binding energy formula does not substantially improve the calculation result.
Published:
Abstract:
Recently a novel four-dimensional Einstein-Gauss-Bonnet (4EGB) theory of gravity was proposed by Glavan and Lin [D. Glavan and C. Lin, Phys. Rev. Lett. 124, 081301 (2020)] which includes a regularized Gauss-Bonnet term by using the re-scalaring of the Gauss-Bonnet coupling constant \begin{document}$\alpha \to \alpha/(D-4)$\end{document} in the limit \begin{document}$D\to 4$\end{document}. This theory also has been reformulated to a specific class of the Horndeski theory with an additional scalar degree of freedom and to a spatial covariant version with a Lagrangian multiplier which can eliminate the scalar mode. Here we study the physical properties of the electromagnetic radiation emitted from a thin accretion disk around the static spherically symmetric black hole in the 4EGB gravity. For this purpose, we assume the disk is in a steady-state and in hydrodynamic and thermodynamic equilibrium so that the emitted electromagnetic radiation is a black body spectrum. We study in detail the effects of the Gauss-Bonnet coupling constant \begin{document}$\alpha$\end{document} in 4EGB gravity on the energy flux, temperature distribution, and electromagnetic spectrum of the disk. It is shown that with the increases of the parameter \begin{document}$\alpha$\end{document}, the energy flux, temperature distribution, and electromagnetic spectrum of the accretion disk all increases. Besides, we also show that the accretion efficiency increases as the growth of the parameter \begin{document}$\alpha$\end{document}. Our results indicate that the thin accretion disk around the static spherically symmetric black hole in the 4EGB gravity is hotter, more luminosity, and more efficient than that around a Schwarzschild black hole with the same mass for a positive \begin{document}$\alpha$\end{document}, while it is cooler, less luminosity, and less efficient for a negative \begin{document}$\alpha$\end{document}.
Published:
Abstract:
The heavy quark effective theory vastly reduces the weak-decay form factors of hadrons containing one heavy quark. Many works attempt to apply this theory to the multiple heavy quarks hadrons directly. In this paper, we examine this confusing application by the instantaneous Bethe-Salpeter method from phenomenological respect, and give the numerical results for the \begin{document}$B_c$\end{document} decays to charmonium where the final states including \begin{document}$1S$\end{document}, \begin{document}$1P$\end{document}, \begin{document}$2S$\end{document} and \begin{document}$2P$\end{document}. Our results indicate that the form factors parameterized by a single Isgur-Wise function deviate seriously from the full ones, especially involving the excited states. The relativistic corrections (\begin{document}$1/m_Q$\end{document} corrections) require the introduction of more non-perturbative universal functions, similarly to the Isgur-Wise function, which are the overlapping integrals of the wave functions with the relative momentum between the quark and antiquark.
Published:
Abstract:
Weakly bound states often occur in nuclear physics. To precisely understand their properties, the coupling to the continuum should be worked out explicitly. In a first step, we use a simple nuclear model in the continuum and on a lattice to investigate the influence of a third particle on a loosely bound state of a particle and a heavy core. Our approach is consistent with the Lüscher formalism.
Published:
Abstract:
In this article, we study the ground states and the first radial excited states of the flavor antitriplet heavy baryon states \begin{document}$\Lambda_Q$\end{document} and \begin{document}$\Xi_Q$\end{document} with the spin-parity \begin{document}$J^P={1\over 2}^{+}$\end{document} by carrying out the operator product expansion up to the vacuum condensates of dimension \begin{document}$10$\end{document} in a consistent way. We observe that the higher dimensional vacuum condensates play an important role, and obtain very stable QCD sum rules with variations of the Borel parameters for the heavy baryon states for the first time. The predicted masses \begin{document}$6.08\pm0.09\,{\rm{GeV}}$\end{document}, \begin{document}$2.78\pm0.08\,{\rm{GeV}}$\end{document} and \begin{document}$2.96\pm0.09\,{\rm{GeV}}$\end{document} for the first radial excited states \begin{document}$\Lambda_b(2{\rm{S}})$\end{document}, \begin{document}$\Lambda_c(2{\rm{S}})$\end{document} and \begin{document}$\Xi_c(2{\rm{S}})$\end{document} respectively are in excellent agreement with the experimental data and support assigning the \begin{document}$\Lambda_b(6072)$\end{document}, \begin{document}$\Lambda_c(2765)$\end{document} and \begin{document}$\Xi_c(2980/2970)$\end{document} to be the first radial excited states of the \begin{document}$\Lambda_b$\end{document}, \begin{document}$\Lambda_c$\end{document} and \begin{document}$\Xi_c$\end{document}, respectively, the predicted mass \begin{document}$6.24\pm0.07\,{\rm{GeV}}$\end{document} for the \begin{document}$\Xi_b(2{\rm{S}})$\end{document} can be confronted to the experimental data in the future.
Published:
Abstract:
The problem of the flat limits of the scalar and spinor fields on the de Sitter expanding universe is considered in the traditional adiabatic vacuum and in the new rest frame vacuum we proposed recently where the frequencies are separated in the rest frames as in special relativity. It is shown that only in the rest frame vacuum the Minkowskian flat limit can be reached naturally for any momenta while in the adiabatic vacuum this limit remains undefined in the rest frames where the momentum vanishes. An important role is played by the phases of the fundamental solutions in the rest frame vacuum which must be regularized in order to obtain the desired Minkowskian flat limits. This procedure fixes the phases of the scalar mode functions and Dirac spinors leading to their definitive expressions derived here. The physical consequence is that in the rest frame vacuum the flat limits of the one-particle operators are just the corresponding operators of special relativity.
Published:
Abstract:
We attempt to clarify several aspects concerning the recently presented four-dimensional Einstein-Gauss-Bonnet gravity. We argue that the limiting procedure outlined in [Phys. Rev. Lett. 124, 081301 (2020)] generally involves ill-defined terms in the four dimensional field equations. Potential ways to circumvent this issue are discussed, alongside some remarks regarding specific solutions of the theory. We prove that, although linear perturbations are well behaved around maximally symmetric backgrounds, the equations for second-order perturbations are ill-defined even around a Minkowskian background. Additionally, we perform a detailed analysis of the spherically symmetric solutions, and find that the central curvature singularity can be reached within a finite proper time.
Published:
Abstract:
The Jiangmen Underground Neutrino Observatory (JUNO) features a 20 kt multi-purpose underground liquid scintillator sphere as its main detector. Some of JUNO's features make it an excellent experiment for \begin{document}$^8$\end{document}B solar neutrino measurements, such as its low-energy threshold, its high energy resolution compared to water Cherenkov detectors, and its much larger target mass compared to previous liquid scintillator detectors. In this paper we present a comprehensive assessment of JUNO's potential for detecting \begin{document}$^8$\end{document}B solar neutrinos via the neutrino-electron elastic scattering process. A reduced 2 MeV threshold on the recoil electron energy is found to be achievable assuming the intrinsic radioactive background \begin{document}$^{238}$\end{document}U and \begin{document}$^{232}$\end{document}Th in the liquid scintillator can be controlled to 10\begin{document}$^{-17}$\end{document} g/g. With ten years of data taking, about 60,000 signal and 30,000 background events are expected. This large sample will enable an examination of the distortion of the recoil electron spectrum that is dominated by the neutrino flavor transformation in the dense solar matter, which will shed new light on the inconsistency between the measured electron spectra and the predictions of the standard three-flavor neutrino oscillation framework. If \begin{document}$\Delta m^{2}_{21} = 4.8\times10^{-5}\; (7.5\times10^{-5})$\end{document} eV\begin{document}$^{2}$\end{document}, JUNO can provide evidence of neutrino oscillation in the Earth at the about 3\begin{document}$\sigma$\end{document} (2\begin{document}$\sigma$\end{document}) level by measuring the non-zero signal rate variation with respect to the solar zenith angle. Moreover, JUNO can simultaneously measure \begin{document}$\Delta m^2_{21}$\end{document} using \begin{document}$^8$\end{document}B solar neutrinos to a precision of 20% or better depending on the central value and to sub-percent precision using reactor antineutrinos. A comparison of these two measurements from the same detector will help understand the current mild inconsistency between the value of \begin{document}$\Delta m^2_{21}$\end{document} reported by solar neutrino experiments and the KamLAND experiment.
Published:
Abstract:
In this paper, we summarize the existing methods of solving the evolution equation of the leading-twist \begin{document}$B$\end{document}-meson LCDA. Then in the Mellin space, we derive a factorization formula with next-to-leading-logarithmic (NLL) resummation for the form factors \begin{document}$F_{A,V}$\end{document} in the \begin{document}$B \to \gamma \ell\nu$\end{document} decay at leading power in \begin{document}$\Lambda/m_b$\end{document}. Furthermore, we investigate the power suppressed local contributions, the factorizable non-local contributions which are suppressed by \begin{document}$1/E_\gamma$\end{document} and \begin{document}$1/m_b$\end{document}, and the soft contributions to the form factors. In the numerical analysis, employing the two-loop-level hard function and jet function we find that both the resummation effect and the power corrections can sizably decrease the form factors. Finally, the integrated branching ratios are also calculated which could be compared with the future experimental data.
Published:
Abstract:
\begin{document}$\beta$\end{document}-decay half-lives of some magic and semi-magic nuclei have been studied in a fully self-consistent Skyrme Hartree-Fock (HF) plus charge-exchange random phase approximation (RPA). The self-consistency is addressed, which means that the same Skyrme energy density functional is adopted in the calculation of ground states and Gamow-Teller excited states. Firstly the impact of \begin{document}${{J}}^2$\end{document} terms on the \begin{document}$\beta$\end{document}-decay half-lives is investigated by using SGII interaction, and a big effect is found. Then the numerical calculations are performed for the selected nuclei with Skyrme energy density functionals SGII, LNS, SKX, and SAMi. Comparisons to available experimental data and predictions of different theoretical models have been discussed.
Published:
Abstract:
We present a dispersive representation of the \begin{document}$\gamma N\rightarrow \pi N$\end{document} partial-wave amplitude based on unitarity and analyticity. In this representation, the right-hand-cut contribution responsible for \begin{document}$\pi N$\end{document} final-state-interaction effects are taken into account via an Omnés formalism with elastic \begin{document}$\pi N$\end{document} phase shifts as inputs, while the left-hand-cut contribution is estimated by invoking chiral perturbation theory. Numerical fits are performed in order to pin down the involved subtraction constants. It is found that good fit quality can be achieved with only one free parameter and the experimental data of the multipole amplitude \begin{document}$E_{0}^+$\end{document} in the energy region below the \begin{document}$\Delta(1232)$\end{document} are well described. Furthermore, we extend the \begin{document}$\gamma N\rightarrow \pi N$\end{document} partial-wave amplitude to the second Riemann sheet so as to extract the couplings of the \begin{document}$N^\ast(890)$\end{document}. The modulus of the residue of the multipole amplitude \begin{document}$E_{0}^+$\end{document} (\begin{document}${\rm S_{11}pE}$\end{document}) is \begin{document}$2.41\rm{mfm\cdot GeV^2}$\end{document} and the partial width of \begin{document}$N^*(890)\to\gamma N$\end{document} at the pole is about \begin{document}$0.369\ {\rm MeV}$\end{document}, which is almost the same as the one of the \begin{document}$N^*(1535)$\end{document} resonance, indicating that \begin{document}$N^\ast(890)$\end{document} strongly couples to \begin{document}$\pi N$\end{document} system.
Published:   , doi: 10.1088/1674-1137/abba13
Abstract:
In this work, the characteristics of \begin{document}$2\nu\beta\beta$\end{document} decays for six nuclei (\begin{document}$^{36}$\end{document}Ar, \begin{document}$^{46}$\end{document}Ca, \begin{document}$^{48}$\end{document}Ca, \begin{document}$^{50}$\end{document}Cr, \begin{document}$^{70}$\end{document}Zn, and \begin{document}$^{136}$\end{document}Xe) in a mass range from \begin{document}$A = 36$\end{document} to \begin{document}$A = 136$\end{document} are performed within the nuclear shell model (NSM) framework. Calculations for the half-lives, nuclear matrix elements (NMEs), phase space factors (\begin{document}$G_{2\nu}$\end{document}), as well as convergence of the NMEs are presented. The theoretical results agree well with the experimental data. In addition, we predict the half-lives of \begin{document}$2\nu\beta\beta$\end{document} decays for four nuclei. We focus on convergence of the NMEs by analyzing the number of contributing intermediate \begin{document}$1^{+}$\end{document} states (\begin{document}$N_{\rm{C}}$\end{document}) for concerned nuclei. We assume \begin{document}$N_{\rm{C}}$\end{document} is safely determined when the accumulated NMEs saturates 99.7% of final calculated magnitude. From the calculations of involved nuclei, we discover a connection between \begin{document}$N_{\rm{C}}$\end{document} and the total number of intermediate \begin{document}$1^{+}$\end{document} states (\begin{document}$N_{\rm{T}}$\end{document}). According to the least square fit, we conclude the correlation is \begin{document}$N_{\rm{C}}=\left( 10.8\pm 1.2\right) \times N_{\rm{T}}^{\left( 0.29\pm 0.02\right)}$\end{document}.
Published:
Abstract:
We revisit the hyperon weak radiative decays in the framework of the non-relativistic constituent quark model. This study confirms the nonlocal feature of the hyperon weak radiative transition operators which are dominated by the pole terms, and an overall self-consistent description of the available experimental data for the Cabibbo-favored hyperon weak radiative decays is achieved. It provides a natural mechanism for evading the Hara theorem, where sizeable parity-violating contributions can come from the intermediate orbital excitations. Cancellations between pole terms also explain significant SU(3) flavor symmetry breaking manifested by the experimental data. We also discuss several interesting selection rules arising from either the electromagnetic or the weak interaction vertices. These features suggest nontrivial relations among different hyperon decays.
Published:
Abstract:
The Hawking-Page phase transitions between the thermal anti-de Sitter vacuum and the charged black holes surrounded by quintessence are studied in the extended phase space. The quintessence field, with a state parameter \begin{document}$-1 < w < -1/3$\end{document}, modifies the temperature and the Gibbs free energy of the black hole. The phase transition temperature \begin{document}$T_{\rm{HP}}$\end{document} and the Gibbs free energy \begin{document}$G$\end{document} are first analytically investigated for the special case with \begin{document}$w=-2/3$\end{document}, and then numerically illustrated for the cases with general \begin{document}$w$\end{document}. The phase transition temperature \begin{document}$T_{\rm{HP}}$\end{document} is found to increase with pressure and to decrease with electric potential. Moreover, \begin{document}$T_{\rm{HP}}$\end{document} is also significantly decreased by the quintessence field, which presents a negative pressure around the black hole.
Published:
Abstract:
We investigate the evolution of abundance of the asymmetric thermal Dark Matter when its annihilation rate at chemical decoupling is boosted by the Sommerfeld enhancement. Then we discuss the effect of kinetic decoupling on relic abundance of asymmetric Dark Matter when the interaction rate depends on the velocity. Usually the relic density of asymmetric Dark Matter is analyzed in the frame of chemical decoupling. Indeed after decoupling from the chemical equilibrium, asymmetric Dark Matter particles and anti--particles were still in kinetic equilibrium for a while. It has no effect on the case of s−wave annihilation since there is no temperature dependence in this case. However, the kinetic decoupling has impacts for the case of p−wave annihilation and Sommerfeld enhanced s− and p−wave annihilations. We investigate in which extent the kinetic decoupling affects the relic abundances of asymmetric Dark Matter particle and anti--particle in detail. We found the constraints on the cross section and asymmetry factor by using the observational data of relic density of Dark Matter.
Published:
Abstract:
We study the emission of fragments in central collisions of light and heavily charged systems of 40Ar+45Sc and 84Kr+197Au, respectively using Quantum Molecular Dynamics (QMD) model as primary model. The fragments are identified using energy based clusterization algorithm i.e., Simulated Annealing Clusterization Algorithm (SACA). The charge distributions of intermediate mass fragments [3≤ \begin{document}$Z_{f}$\end{document} ≤12] are fitted with power-law ( \begin{document}$\propto Z_{f} ^{-\tau}$\end{document} ) and exponential fits ( \begin{document}$\propto {\rm{e}} ^{-\lambda {Z_{f}}}$\end{document} ) to extract the parameters τ and \begin{document}$\lambda$\end{document} whose minimum value is also sometimes linked with the onset of fragmentation or critical point for a liquid-gas phase transition. Other parameters such as normalized second moment \begin{document}$<S_2>$\end{document} , \begin{document}$<\gamma_2>$\end{document} , average size of the second largest cluster \begin{document}$<Z_{\rm max2}>$\end{document} , phase separation parameter ( \begin{document}$S_p$\end{document} ), bimodal parameter (P), information entropy (H) and Zipf's law are also analyzed to find the exact energy of the onset of fragmentation. Our detailed analysis predicts an energy point to exist between 20-23.1 MeV/nucleon which is very close to experimentally observed value of 23.9 MeV/nucleon for 40Ar+45Sc reaction. We also found that the critical energy deduced using Zipf's law is higher than predicted from other critical exponents. Also, no minimum is found in τ values for the highly charged system of 84Kr+197Au in agreement with experimental findings and various theoretical calculations. We observe that QMD + SACA model calculations are in agreement with the experimental observations. This agreement supports our results regarding the energy point of the liquid-gas phase transition or the onset of fragmentation.
Published:   , doi: 10.1088/1674-1137/abae56
Abstract:
The 12C+12C fusion reaction plays a crucial role in stellar evolution and explosions. Its open reaction channels mainly include \begin{document}$\alpha$\end{document}, p, n, and 8Be. Despite more than a half century of efforts, large discrepancies remain among the experimental data measured using various techniques. In this work, we analyze the existing data using the statistical model. Our calculation shows: 1) the relative systematic uncertainties of the predicted branching ratios get smaller as the predicted ratios increase; 2) the total modified astrophysical S-factors (S* factors) of the p and \begin{document}$\alpha$\end{document} channels can each be obtained by summing the S* factors of their corresponding ground-state transitions and the characteristic \begin{document}$\gamma$\end{document} rays while taking into account the contributions of the missing channels to the latter. After applying corrections based on branching ratios predicted by the statistical model, an agreement is achieved among the different data sets at Ecm>4 MeV, while some discrepancies remain at lower energies suggesting the need for better measurements in the near future. We find that the recent S* factor obtained from an indirect measurement is inconsistent with the direct measurement at energies below 2.6 MeV. We recommend upper and lower limits for the 12C+12C S* factor based on the existing models. A new 12C+12C reaction rate is also recommended.
Published:
Abstract:
The transonic phenomenon of black hole accretion and the existence of the photon sphere are the characteristics of strong gravitational fields near a black hole horizon. In this work, we study spherical accretion flow onto a general parametrized spherically symmetric black hole spacetimes. For this purpose, we analyze the accretion process of various perfect fluids, such as the isothermal fluid of ultra-stiff, ultra-relativistic, and sub-relativistic types and polytropic fluid, respectively. The influences of extra parameters beyond the Schwarzschild black hole in the general parameterized spherically symmetric black hole on the flow behaviors of the above-mentioned test fluids are studied in detail. In addition, by studying the accretion of ideal photon gas, we further discuss the correspondence between the sonic radius of accreting photon gas and the photon sphere for the general parameterized spherically symmetric black hole. Some possible future extensions of our analysis are also discussed.
Published:
Abstract:
We investigate the bulk viscosity of strange quark matter in the framework of equivparticle model, where analytical formulae are obtained for certain temperature ranges and can be readily applied to those with various quark mass scalings. In the case of adopting a quark mass scaling with both linear confinement and perturbative interactions, the obtained bulk viscosity increases by \begin{document}$1 \sim 2$\end{document} orders of magnitude comparing with bag model scenarios. Such an enhancement is mainly due to the large quark equivalent masses adopted in the equivparticle model, which essentially attribute to the strong interquark interactions and are related to the dynamical chiral symmetry breaking. Due to the large bulk viscosity, the predicted damping time of oscillations for canonical 1.4 \begin{document}${\rm{M}}_\odot$\end{document} strange star is less than one millisecond, which is faster than previous findings. Consequently, the obtained \begin{document}$r$\end{document}-mode instability window for the canonical strange stars well accommodates the observational frequencies and temperatures for pulsars in the low-mass X-ray binaries (LMXBs).
Published:
Abstract:
Scrupulous theoretical study of 8Be nucleus states, both clustered and non-clustered, is performed over a wide range of the excitation energies. The quantities which characterize the degree of the alpha-clustering of these states: spectroscopic factors, cluster form factors as well as the alpha-decay widths are computed in the framework of an accurate ab initio approach developed. Other basic properties of 8Be spectrum: the binding and excitation energies, mean values of the isospin are calculated simultaneously. In the majority of instances the results of the computations turn out to be in a good agreement with the spectroscopic data. A number of predictions are made and corresponding verification experiment is proposed. Prospects of the developed approach for nuclear spectroscopy are demonstrated.
Published:
Abstract:
Motivated by the problem of expanding single-trace tree-level amplitude of Einstein-YangMills theory to the BCJ basis of Yang-Mills amplitudes, we present an alternative expansion formula in the gauge invariant vector space. Starting from a generic vector space consisting of polynomials of momenta and polarization vectors, we define a new sub-space as gauge invariant vector space by imposing constraints of gauge invariant conditions. To characterize this sub-space, we compute its dimension and construct an explicit gauge invariant basis from it. We propose an expansion formula in the gauge invariant basis with expansion coefficients being linear combinations of Yang-Mills amplitude, manifesting the gauge invariance of both expansion basis and coefficients. With help of quivers, we compute the expansion coefficients via differential operators and demonstrate the general expansion algorithm by several examples.
Published:
Abstract:
The Circular Electron Positron Collider (CEPC) proposed as a future Higgs boson factory will operate at a center-of-mass energy of 240 GeV and accumulate 5.6 ab-1 of integrated luminosity in 7 years. In this paper, we estimate the upper limit of BR(\begin{document}$H \rightarrow$\end{document} inv) for three independent channels including two leptonic channels and one hadronic channel at the CEPC. Based on the full simulation analysis, the upper limit of BR(\begin{document}$H \rightarrow$\end{document} inv) could reach 0.26% at the 95% confidence level. In the Stand Model (SM), the Higgs boson can only decay invisibly via \begin{document}$H\rightarrow ZZ^\ast\rightarrow\nu\overline{\nu}\nu\overline{\nu}$\end{document}, so any evidence of invisible Higgs decays that exceeds BR(\begin{document}$H \rightarrow$\end{document} inv) of SM will indicate a phenomenon that is beyond the SM (BSM). The invariant mass resolution of visible hadronic decay system \begin{document}$ZH(Z \rightarrow qq$\end{document}, \begin{document}$H \rightarrow$\end{document} inv) is simulated and the physics requirement at the CEPC detector to reach this is given.
Published:
Abstract:
We use a geometric model for hadron polarization in heavy ion collisions with an emphasis on the rapidity dependence. The model is based on the model of Brodsky, Gunion, and Kuhn and that of the Bjorken scaling. We make predictions for the rapidity dependence of global \begin{document}$\Lambda$\end{document} polarization in the collision energy range 7.7-200 GeV by taking assumed rapidity dependence of two parameters \begin{document}$\kappa$\end{document} and \begin{document}$\left\langle p_{T}\right\rangle$\end{document}. The predictions can be tested by the future beam-energy-scan experiments at Relativistic Heavy Ion Collider of Brookhaven National Lab.
Published:   , doi: 10.1088/1674-1137/44/5/055101
Abstract:
We construct an alternative uniformly accelerated reference frame based on 3+1 formalism in adapted coordinate. It is distinguished with Rindler coordinate that there is time-dependent redshift drift between co-moving observers. The experimentally falsifiable distinguishment might promote our understanding of non-inertial frame in laboratory.